Monday, November 9, 2009
The concept of Gray Component Replacement (GCR) has been around for years but seems to have caught fire recently among commercial printers and newspaper publishers because of technological advancements. Ink savings of up to 20% have been reported on jobs having heavy four-color ink coverage.
Some magazine publishers and other print buyers have negotiated lower ink costs by applying, or allowing a printer to apply, GCR to their prepress files.
Explaining GCR requires a brief lesson in color theory: When combined, red light, green light, and blue light create white light, which is why they are called the three primary colors.
Ink is a filter for light being reflected off of paper. Cyan blocks red, magenta filters out green, yellow blocks blue, and black filters out all three primary colors. You can create a heavy black area with 100% coverage each of cyan, magenta, and yellow. But you could use less expensive ink, and less of it, if you just printed the area in 100% black.
In theory, GCR can take an area that is 60% cyan, 60% magenta, 40% yellow, and 0% black and create the same color at lower cost by converting it to something along the lines of 20%C-20%M-0%Y-40%K. But such “heavy GCR” can lead to a variety of print-quality problems.
That's why most printers use a GCR program that is less radical in substituting black ink for the chromatic inks, as shown in the image above (taken from Gordon Pritchard's Quality in Print blog.) The graphic shows a traditional separation on the left and a GCR separation on the right.
Besides the ink savings, printers and software vendors tout such benefits of GCR as faster makereadies, shorter drying times, less ink slinging, less paper waste, more efficient use of the earth's resources, and more stable color throughout a press run.
“For many printers, the increased color stability is a perfect compliment to the industry trend for a ‘by the numbers’ print manufacturing process,” Pritchard says in his excellent and well illustrated eight-part series on GCR. (To read the series, go to this link and then scroll down past the first two articles.)
The vast majority of print buyers pay for ink by the page rather than by the pound, so they don’t automatically reduce their ink costs by using GCR. But some have been able to negotiate lower ink costs by switching to GCR, with the printer in some cases getting a share of the savings.